In Go, parameters to functions are passed only by value.

Go pass parameters by value

In the following example, an integer and a User structure are passed as parameters to functions.

package main

import "fmt"

type User struct {
    name       string
    occupation string
}

func main() {

    x := 10
    fmt.Printf("inside main %d\n", x)

    inc(x)

    fmt.Printf("inside main %d\n", x)

    fmt.Println("---------------------")

    u := User{"Raj", "Engineer"}
    fmt.Printf("inside main %v\n", u)

    change(u)
    fmt.Printf("inside main %v\n", u)
}

func inc(x int) {

    x++
    fmt.Printf("inside inc %d\n", x)
}

func change(u User) {

    u.occupation = "driver"
    fmt.Printf("inside change %v\n", u)
}

Output:

inside main 10
inside inc 11
inside main 10
---------------------
inside main {Raj Engineer}
inside change {Raj driver}
inside main {Raj Engineer}

In the above example, the original values of the x and User struct are not modified.

A copy of the integer value is created. Inside the function, we increment the value of this copy. So the original variable is intact.

func inc(x int) {

    x++
    fmt.Printf("inside inc %d\n", x)
}